"Some of you are alright. Don't go to campus tomorrow," the post said.

Yik Yak is a social media app that allows users to share anonymous messages, or Yaks, with others in a five-mile radius. However, the man police say they arrested early Wednesday for posting threats on Yik Yak and other social media -- Hunter M. Park, 19 -- was "contacted" in Rolla, more than 90 miles south of Columbia.